Four new species of deep water agglutinated foraminifera from the Oligocene-Miocene of the Congo Fan (offshore Angola)

Four new species of deep-water agglutinated benthic foraminifera are described from the Oligocene and Miocene of the Congo Fan, offshore Angola. Scherochorella congoensis n.sp., Paratrochamminoides goroyskiformis n.sp., Haplophragmoides nauticus n.sp. and Portatrochammina profunda n.sp. all occur in deep-sea turbiditic shales and sands from the distal section of the Congo Fan

Miocene deep-water agglutinated Foraminifera from ODP Hole 909c: Implications for the paleoceanography of the Fram Strait Area, Greenland Sea

Deep-water agglutinated Foraminifera (DWAF) are investigated from Miocene sediments recovered from ODP Hole 909C in the Fram Strait, Norwegian-Green land Sea. We studied 125 samples from Cores 909C-50R to -103R. and recovered over 60 species of DWAF. The faunal succession in Hole 909C is subdivided into three assemblages based on the stratigraphic ranges of characteristic cosmopolitan taxa. These are: (1) a diverse Reticulophraginium amplectens - Reophanus berggreni Assemblage in Cores 909C-100R-2 to -91R-1 (1040.71-952.78mbsf); (2) a Reticulophragmium amplectens Assemblage in Cores 909C-87R-2, to -71R-3 (915.7-762.68mbsf); and (3) a low-diversity Reticulophraginium rotundidorsatum Assemblage in Cores 909C-71R-1 to -55R-1 (759.68-605.52mbsf). The DWAF assemblages are correlated to the standard chronostratigraphy using dinoflagellate cysts and magnetostratigraphy. The stratigraphic ranges of some well-known Palcogene DWAF species extend far into the Miocene at this locality, confirming tire hypothesis that the Arctic and northern Norwegian Sea basins served as a refuge for these species long after they disappeared from the North Atlantic stratigraphic record. The taxonomic affinities of the Miocene assemblages from Hole 909C supports the idea that an estuarine Circulation pattern has been in place between the Arctic Ocean and Greenland Sea basins since at least the early Miocene. Changes in the benthic foraminiferal morphogroups within the R. rotundidorsatum Assemblage correlate with an increase in total organic carbon, indicating an increase in oceanic productivity in the Fram Strait region during the late Miocene

Miocene deep-water agglutinated foraminifera from the Lomonosov Ridge and the opening of the Fram Strait

Deep-water agglutinated Foraminifera (DWAF) were recovered from Miocene to Pliocene sediments in 103 samples from IODP Hole M0002A on the Lomonosov Ridge. The First Occurrence of DWAF in Hole M0002A is observed just above the color change corresponding to the boundary between Lithological Subunits 1/4 and 1/5 in Core section –44X-1. The foraminiferal record of Hole M0002A consists entirely of agglutinated benthic species, largely sparse assemblages containing Cyclammina pusilla and Alveolophragmium polarensis. The faunal succession in Hole M0002A is subdivided into three assemblages based on the stratigraphic ranges of characteristic taxa: (1) a relatively diverse assemblage at the base of Lithological Subunit 1/4 (Cores 44X-1 to –38X), with abundant agglutinated foraminifera including Reticulophragmium pusillum and Ammolagena clavata, indicating connections with the North Atlantic. This assemblage displays the best preservation, which is here attributed to higher concentrations of dissolved silica in pore waters (2) A less diverse assemblage characterized by Alveolophragmium polarensis with Adercotryma agterbergi, in the lower part of Lithological Subunit 1/3 (Cores –38X to –35X); (3) a sparse residual assemblage within Lithological Subunit 1/3 with Rhabdammina spp., A. polarensis and R. pusillum indicating poor preservation of organically-cemented DWAF in Cores –34X to –10X. A comparison of the DWAF assemblages from the Lomonosov Ridge with previously studied Miocene assemblages from ODP Hole 909C in the Fram Strait, Norwegian-Greenland Sea (Kaminski et al. 2005), suggests that the inflow of Atlantic intermediate water into the Arctic Ocean began prior to 17.5 Ma

Early to middle Miocene foraminifera from the deep-sea Congo Fan, offshore Angola

Analysis of a 630m section of an exploration well penetrating the distal part of the Congo Fan (~2000m water depth) yielded high abundance and diversity assemblages of agglutinated and calcareous benthic foraminifera. Planktonic foraminifera constrain the age to Early – Middle Miocene, and \delta 18O records reveal the Mi1 (~16.3 Ma) isotopic shift. Relatively few taxonomic studies of deep-water calcareous and agglutinated benthic foraminifera exist from this time period in this locality. All species encountered are therefore taxonomically described and documented using SEM photography (over 170 species), along with 27 species of planktonic foraminifera. Faunas show close affinities to those of the eastern Venezuela Basin, Gulf of Mexico and Central Paratethys. Seven assemblages are defined and analysed using morphogroup analysis and Correspondence Analysis, documenting the response of benthic foraminifera to three primary environmental-forcing factors; energy levels in the benthic boundary layer, oxygen levels relating to changing surface water productivity, and fluctuations in the level of the CCD. Near the top and bottom of the studied section both foraminiferal abundance and diversity decrease, corresponding with increased sand content implying greater energy levels and environmental disturbance. The majority of the section consists of shales with very low percentage sand, high foraminiferal abundance and diversity, and high sedimentation rates of ~10cm/kyr. Morphogroup analysis reveals a major switch in the fauna at around oxygen isotope event Mi1, with the transition from an epifaunal-dominated Cibicidoides assemblage to shallow infaunal-dominated Bulimina assemblage. We regard this as likely due to expansion of the oxygen minimum zone (paleobathymetric estimates are ~1000m) related to increased surface-water productivity and global cooling. Shifts in calcareous foraminiferal percentage over the studied interval overprint these signals and are believed to be related to a shoaling CCD, linked to reduced oceanic acidity and global atmospheric CO2 levels during the early Middle Miocene Monterey Carbon Isotope Excursion

Karreriella perforata n. sp. : a new Pliocene agglutinated benthic foraminifer with a perforated wall structure from the southern Bering Sea

This is the final version of the article. Available from the Grzybowski Foundation via the link in this record.We describe a new agglutinated benthic foraminiferal species from the Pliocene of Hole U1341B drilled in the southern Bering Sea during IODP Expedition 323. The calcareous-cemented species Karreriella perforata n.sp. is coarsely canaliculated, with regularly-spaced straight, unbranched pores that are open to the test surface. This feature of the test wall is rare among agglutinated foraminifera, and is interpreted as a morphological adaptation to enable survival in the strongly hypoxic environment present in the deep Bering Sea.We are grateful for the support provided by King Abdulaziz City for Science and Technology (KACST) through the Science and Technology Unit at King Fahd University of Petroleum & Minerals (KFUPM) for partially funding this work under project No. 11-ENV1613-04 as part of the National Science, Technology, and Innovation Plan

Do volcanoes trigger climate change?

This is the final version of the article. Available from NERC via the URL in this record.Huge volcanic eruptions may have pushed the climate from global warming to global cooling 16 million years ago. The theory could have big implications for efforts to slow climate change by fertilising plankton in the ocean. Sev Kender, Victoria Peck and John Smellie explain

Foraminifera from the Eocene variegated shales near Barwinek (Magura unit, Outer Carpathians), the type locality of Noth (1912) revisited

This is the final version of the article. Available from the Polish Geological Society via the URL in this record.A rich deep-water agglutinated foraminifera (DWAF) fauna (approximately 50 taxa) is documented from the lower to middle Eocene Variegated Shales of the Magura Unit, Outer Carpathians. Four localities have been sampled from the Barwinek region, which are thought to correspond to those studied by Rudolf Noth in 1912. A stream section of variegated red and green shales outcrop near Zyndranowa (Poland), was logged and extensively sampled. A further two outcrops of red shales were sampled in stream sections near Vyšny Komarnik (Slovakia), and a stream section close to Olchowiec (Poland). The DWAF recovered closely resemble assemblages of the same age in localities throughout the Carpathians. The material under study in this report has been correlated using the first appearance of Reticulophragmium amplectens, dating the samples early Middle Eocene. Two DWAF assemblages have been differentiated. The 'Rhabdammina Assemblage' is found mainly in green shales and is thought to be indicative of a high-energy slope or deep sea fan environment slightly reduced in oxygen; and the 'Paratrochamminoides Assemblage' is found mainly in red shales and is thought to be indicative of a well-oxygenated condensed sequence. The two faunas are otherwise very similar in composition. Of the seven new species described by Noth in 1912, one has been identified in this report and re-described as Paratrochamminoides deflexiformis (Noth).This study was originally carried out as an MSc project in Micropalaeontology at U.C.L. We would like to thank AAPG student Grants-in-Aid programme and the EEC-Socrates programme for the essential funding provided in support of this projec

Oligocene Deep-Water Agglutinated Foraminifera from the Congo Fan, Offshore Angola: Palaeoenvironments and Assemblage Distributions

Seventh International Workshop on Agglutinated Foraminifera, Urbino, Italy, October 2-8, 2005Agglutinated foraminiferal assemblages from the Oligocene section of an exploration well drilled in the distal part of the Congo Fan are fully documented and interpreted for palaeoenvironment. A total of 65 ditch cutting samples were analysed at 10 m intervals, from 3630 to 4270 m below rotary table. An average of 170 specimens were extracted per sample, with over 100 species being documented and described using SEM and light photography. The results reveal the most taxonomically diverse deepsea Oligocene fauna yet described. Six assemblages have been defined and analysed with Correspondence and 'Morphogroup' Analysis. These are 1. Nothia robusta / Reticulophragmium Assemblage (4110-4270 m), 2. Nothia robusta / Scherochorella congoensis / Discamminoides sp. 1 Assemblage (4000-4100 m), 3. High diversity Reticulophragmium Assemblage (3870-3990 m), 4. Portatrochammina profunda Assemblage (3790-3860 m), 5. Nothia latissima Assemblage (3730-3780 m) and 6. Low abundance Assemblage (3630-3720 m). Palaeobathymetric estimates range from middle - lower bathyal based on comparison with living taxa and morphogroup distributions. These results extend the known stratigraphic range (last occurrences) of Reticulophragmium amplectens into the Oligocene in the Atlantic, and possibly also Paratrochamminoides gorayskii, Paratrochamminoides olszewskii, Trochamminoides aff. proteus, Trochamminoides subcoronatus, Haplophragmoides horridus and Haplophragmoides walteri, although reworking is documented with these species. Results also extend the known first occurrences of Recurvoides azuaensis, Spiropsammina primula, Cyclammina aff. orbicularis, Discamminoides sp. and Glaphyrammina americana into the Oligocene. Large scale variations within faunas are largely assigned to documented variations in sand content, where higher proportions of sand generally coincide with reduced diversity and abundance along with a dominance of opportunistic species such as Nothia robusta, Nothia latissima and Ammodiscus latus. A major excursion in the infaunal morphogroup, suspension-feeding morphogroup and diversity and abundance within Assemblage 2 is termed the 'Scherochorella Event', and does not correlate with an increase in sand. This fauna is thought to be the result of lower oxygen conditions allowing the dominance of the low oxygen morphotype Scherochorella congoensis and the opportunistic species Nothia robusta. Deep-water circulation in the Atlantic at this time is generally thought to have been strong, and this event suggests that there may have been a temporary expansion of the oxygen minimum zone during the Late Oligocene, coinciding with increased benthic δ18O values, global cooling, and increased upwelling associated with a stronger polar front. The otherwise high diversity of the fauna in the well supports the interpretation of well-oxygenated conditions.We would like to thank BP Exploration for their support in fully funding this project

Foraminiferal characterisation and taxonomy of Oligocene-Miocene Congo Fan deep sea sub-environments, offshore Angola.

The Congo Fan has been accumulating sediment since the mid-Oligocene, and is of particular interest to the oil industry due to abundant large reservoirs contained within the meandering sandy palaeochannels from largely Miocene and Oligocene deposits. The high sedimentation rates and rich benthic foraminiferal faunas also provide an interesting record of Miocene and Oligocene palaeoceanographic change in the southeast Atlantic, a stratigraphic time interval that has had no recovery from proximal ODP and DSDP Sites. Three oil wells spanning the Upper Oligocene to Middle Miocene from the distal part of the Congo Fan (Block 31, approximately 2000 m water depth) are studied for both benthic and planktonic foraminifera using ditch cutting samples at 10 m spacing. In addition to assemblage data, 8,80 and 813C measurements have been obtained from Cibicidoides spp. for the Miocene which, along with several planktonic foraminiferal datums, provides a relatively well-constrained age model. The Oligocene sections are dominated by agglutinated benthic foraminifera and the age model is less accurate. A full taxonomy has been carried out on all foraminifera encountered, with over 150 agglutinated, 80 calcareous benthic, and 27 planktonic species described and pictured. A number of sedimentological environments contain characteristic faunas. Channel deposits are either barren or contain current-sorted calcareous specimens, levee deposits have higher abundances of transported calcareous specimens and are affected by hydrodynamic sorting, overbank deposits are dominated by high diversity in situ agglutinated faunas. Oligocene sediments from the Congo Fan consist almost entirely of agglutinated foraminifera due to deposition below a locally raised CCD. A level of decreased diversity and increased abundance (the 'Scherochorellcf event) in the intra-Upper Oligocene records a probable expansion of the oxygen minimum zone associated with polar cooling. During the Early Miocene a gradual and persistent increase in the percentage of calcareous foraminifera is mirrored by increasing benthic 813C, suggesting reduced bottom-water acidification and a lowering of the CCD. A dramatic shift in the shallow infaunal morphogroup (-16 Ma) indicates lower oxygen and a second episode of oxygen minimum zone expansion, which is coincident with cooling in this location and adds evidence for raised colder bottom waters. Global cooling at this time was probably responsible for increasing the strength of the polar front, and in turn strengthening offshore winds affecting an increase in upwelling and surface water productivity